It is clear that a person of a certain descent may become
attached to people of another descent, either because he feels
well-disposed toward them, or because there exists an (old) alliance or
client(-master) relationship, or yet because he had to flee from his own
people by reason of some crime he committed. Such a person comes to be
known as having the same descent as those (to whom he has attached
himself) and is counted one of them with respect to the things that
result from (common descent), such as affection, the rights and
obligations concerning talion and blood money, and so on. When the
things which result from (common) descent are there, it is as if (common
descent) itself were there, because the only meaning of belonging to one
or another group is that one is subject to its laws and conditions, as
if one had come into close contact with it. In the course of time, the
original descent is almost forgotten. Those who knew about it have
passed away, and it is no longer known to most people. Family lines in
this manner continually changed from one tribal group to another, and
some people developed close contact with others (of a different
descent). This happened both in pre-Islamic and in Islamic times, and
between both Arabs and non-Arabs. If one studies the different opinions
concerning the pedigree of the family of al-Mundhir 56and others, the matter will become somewhat clearer.

The affair of the Bajilah and 'Arfajah b. Harthamah is
an(other) illustration. When 'Umar appointed 'Arfajah their governor,
(the Bajilah) asked ('Umar) to withdraw him, saying that he was a nazif 57among them, that is, one who had come to them from
outside and attached himself to them. They asked that he appoint Jarir
(instead). 'Umar asked 'Arfajah about this, and he replied: "They are
right, O Commander of the Faithful. I am from the Azd. I shed blood
among my people, and joined (the Bajilah)." 58This shows how 'Arfajah had come to mix with
the Bajilah, had become of their skin, and was known as one having the
same descent as they, to the extent that he could eventually become a
candidate for leadership over them, (and would have) had someone not
remembered the genealogical ramifications. Had they overlooked it and
had (still) more time elapsed, (his foreign origin) would have been
forgotten, and he would have been considered one of them in every
respect.

This should be understood and pondered as one of God's
ways with His creatures. Similar things occur frequently in our own
times, and have always been frequent in former times.59